I hear from a lot of fiction writers concerned about writing credits. You’ve been told over time that in order to get published you need to build writing credits or are concerned that when it comes to your query you don’t have much to add in terms of your bio. Don’t worry about it. Everyone has to start somewhere, and I think all agents realize this. We don’t require writing credits and certainly don’t expect them. There are plenty of authors out there—heck, there are plenty on my own list—who never published anything until that first book.
That being said, if you are getting writing credits somewhere—reputable literary magazines, epublishers, or even nonfiction venues like newspapers—you should definitely mention that. The life and travels of a writer don’t neatly fit in a box. In other words, if you see yourself as a romance writer now, it doesn’t mean that you were writing romance three years ago, and your credits might reflect that. Writing credits of any kind show that others have acknowledged your writing ability and also show that you are serious about pursuing writing as a career and not just checking out publishing to see what might happen (and we get a lot of people who do that).
If you have fairly recent credits (a contest from third grade doesn’t count), definitely mention them no matter what they are. Remember, querying agents is like sending out a resume. Your goal is to make yourself stand out from the pack and anything you have that can help that is worth mentioning.